This invention relates generally to a monomeric plasticizer for halogen-containing resins which has permanence (low volatility), low temperature flexibility, high efficiency and good alkane extraction resistance. More particularly, this invention relates to monomeric plasticizers based upon mixed esters of terephthalic acid or trimellitic acid.
A plasticizer has been defined as a material which is admixed with a plastic to increase its workability, flexibility and distensibility. The addition of a plasticizer to a plastic may lower the melt viscosity, the second order transition temperature, or the elastic modulus of the plastic.
Phthalic acid esters of monoalcohols have been widely used as plasticizers. These esters are produced by condensing aliphatic mono-alcohols containing not more than 20 carbon atoms with phthalic anhydride to form neutral products.
Dioctylphthalate, also known as DOP, is widely accepted for use in plasticizing polyvinyl chloride. It accounts for nearly one-fourth of all plasticizers produced. Since plasticization of polyvinyl chloride requires an estimated 80 percent of plasticizer production, DOP is used as a benchmark for plasticizer price/performance. In other words, acceptance of a plasticizer largely depends upon its being less expensive than DOP or its doing some specific job better than DOP.
Di-esters of ortho-phthalic acid are commonly used as plasticizers for chlorine containing polymers such as polyvinyl chloride. The esters are usually derived from alkanols containing 4 to 14 carbon atoms, e.g., iso-octanol, 2-ethyl hexanol, iso-decanol and the like.